Mongabay (mongabay.com) is an American conservation news web portal that reports on environmental science, energy, and green design, and features extensive information on tropical rainforests, including pictures and deforestation statistics for countries of the world.

It was founded in 1999 by economist Rhett Ayers Butler in order to increase "interest in and appreciation of wildlands and wildlife, while examining the impact of emerging local and global trends in technology, economics, and finance on conservation and development". In recent years, to complement its US-based team, Mongabay has opened bureaus in Indonesia, Latin America, and India, reporting daily in Indonesian, Spanish and English respectively. Mongabay's reporting is available in nine languages.

In an interview with Conjour, Butler said his passion for rainforests drove him to start Mongabay: "I was intrigued by the complexity of these ecosystems and how every species seemed to play a part. As I became more passionate about rainforests, I grew more concerned about their fate, including the threats they face."

The founder of the website explains that "mongabay" originated from an anglicized spelling and pronunciation of Nosy Mangabe, an island off the coast of Madagascar. He goes on to note that it is best known as "a preserve for the aye-aye, a rare and unusual lemur famous for its bizarre appearance".

Mongabay.com is independent and unaffiliated with any organization. The site has been used as an information source by CNN, CBS, the Discovery Channel, NBC, UPI, Yahoo!, and other such outlets.

All of Mongabay's content is free to access on its site, thanks to the volumes of visitors per month - as of January 2008, 2.5 million. In 2008, Butler said that the traffic brought the site $15,000 to $18,000 a month from AdSense, but the decline in advertising revenue across the environmental media sector after the 2008 financial crisis, sharply reduced the site's income. In 2012, Butler launched mongabay.org, a 501(c)(3) organization, to support Mongabay's education program and non-English reporting initiatives as well as expand its environmental reporting initiatives, including grants for journalists. Mongabay phased out advertising on its news content in 2017.

Mongabay.com formerly published Tropical Conservation Science, a peer-reviewed, open-access academic journal on the conservation of tropical forests and of other tropical ecosystems. Since its inception in 2008, it has four issues a year, in March, June, September, and December. It used to provide opportunities for scientists in developing countries to publish their research in their native languages, but as of September 2012, Tropical Conservation Science publishes papers only in English. It has been published by SAGE Publications since August 2016 and Mongabay no longer has any affiliation.

On May 19, 2012, Mongabay.com launched an Indonesian language affiliate. In June 2016, Mongabay launched a Spanish-language news service in Latin America. And in January 2018, an Indian website was launched. In 2019, Mongabay established Mongabay-Brasil, a Portuguese-language bureau staffed by Brazilians. Those were followed by Hindi and French sites.